The functional and structural importance of hydrophobic associations within the electron transport system of the mitochondrial inner membrane will be characterized by studying two of its major electron transport complexes, cytochrome bc1 and cytochrome c oxidase. The individual protein-lipid complexes and their purified subunis, e.g., cytochrome b and cytochrome c1 will be investigated, with specific emphasis upon: 1) the functional importance of tightly bound phospholipids, particularly tightly bound diphosphatidyl glycerol; 2) the structural alterations that are caused by the removal of this tightly bound lipid; 3) the molecular size, shape and possible asymmetry of isolated subunits; and 4) the possible domain structure of the isolate subunits, particularly cytochrome b and cytochrome c1. The approach will be to use phospholipid and detergent exchange, detergent binding, hydrodynamic physical measurements and limited proteolysis to investigate these structural and functional features of the complexes. The long range goal of this project s to identify the hydrophobic interactions that are essential for coupled electron transport within the mitochondrial inner membrane and to characterize the functional importance of the protein-lipid interface between intrinsic membrane proteins and the apolar interior of membranes.